The invention relates to a method for reducing restoring forces of package sleeves in a filling machine, wherein each flat-folded package sleeve comprises four package walls separated from one another by parallel-running outer and inner fold edges and at the outer fold edges respectively one acute internal angle is enclosed between the package walls, comprising the process steps                inserting flat-folded package sleeves into a magazine of the filling machine,        removing respectively one flat-folded package sleeve from the magazine and        unfolding the flat-folded package sleeve to form an upright package sleeve forming a parallelogram in cross-section by means of a removal and unfolding apparatus and        transferring the upright package sleeve by means of a transfer apparatus to a transport device for transporting the upright package sleeve along a transport path, where at least one processing step is carried out on the upright package sleeve whilst the upright package sleeve is located on the transport path of the transport device.        
Filling machines for filling products, in particular liquid foodstuffs, into packaging containers consisting of cardboard composite material are known from the prior art. For the structure of known filling machines, reference is made, for example, to EP 0 936 992 B1 and DE 41 42 167 C2.
On account of better transportability, the usually rectangular packaging containers are only produced in the filling machine from packaging blanks provided with fold edges and welded together to form package sleeves. Each flat-folded package sleeve has four package walls separated from one another by four parallel-running outer and inner fold edges. At the outer fold edges of the flat-folded package sleeve, an acute angle is enclosed in each case between the package walls. The inner fold edges of the flat-folded package sleeve are disposed between the outer fold edges. At the inner fold edges of the flat-folded package sleeve, an obtuse internal angle is enclosed in each case between the package walls. If the package walls have the same dimensions, the inner fold edges divide the section between the outer fold edges at the centre.
The flat-folded package sleeves from a magazine are supplied to the at least one conveyor line of the filling machine. In the magazine the package sleeves are disposed consecutively as stacks, usually upright. On a removal side of the magazine pointing in the direction of the conveyor line, two of the four package walls of the respectively front package sleeve are exposed. On its rear side the stack is acted upon by a force in the direction of the removal side, for example, that of a spring or a linear drive in order to displace the package sleeves of the stack towards the removal side.
A removal and unfolding apparatus comprises a gripper for gripping one of the two package walls exposed on the removal side of the magazine, a guide for the other one of the two exposed package walls and retaining elements disposed in the direction of movement after the guide for receiving the outer fold edges of the unfolded package sleeve.
The removal and unfolding apparatus unfolds the initially flat-folded package sleeve to form a package sleeve forming a rectangle in cross-section. The unfolded package sleeve is transferred by a transport device. Along the conveyor line of the filling machine, the packaging containers produced from the package sleeves are sterilised, filled and then closed. The package base is usually produced directly before filling. Then the package top is usually produced.
In particular, transport wheels or revolving conveyor belts having pocket-shaped receptacles for the unfolded package sleeves or packaging containers are used as the transport device. The stepwise rotating transport wheels have a plurality of radially outwardly extended parallel receptacles. The receptacles are usually configured as mandrels onto which the unfolded package sleeves or packaging containers are slid; we then talk of a mandrel wheel. In another embodiment of such a transport wheel, each receptacle has a plurality of arms or profiles which come to rest on the outer side, in particular directly adjacent to the fold edges of the unfolded package sleeve or the packaging container. In this case, the receptacles form cells into which the unfolded package sleeves or packaging containers can be inserted; we then talk of a cell wheel.
A filling machine with removal and unfolding apparatus pertaining to the prior art, made by SIG Combibloc GmbH, D-52441 Linnich is explained in detail hereinafter with reference to FIG. 1a)-d):
The flat-folded package sleeves (1) are stored upright in the magazine (2) of the filling machine. Each flat-folded package sleeve (1) has four package walls (5a, 5b, 6a, 6b) separated from one another by parallel running outer fold edges (3a, 3b) and inner fold edges (4a, 4b).
A removal side (7) of the magazine (2) exposes the two forwardly pointing package walls (5a, 5b) of the respectively front package sleeve (1). In order that the package sleeves (1) do not fall out of the magazine on the removal side (7), retaining elements (8a, 8b) are disposed on the removal side (7), which elements extend along the outer fold edges (3a, 3b) of the front package sleeve (1). The respectively front package sleeve (1) is not removed in the full width of the two package walls (5a, 5b). On the contrary, the package sleeve (1) is merely gripped at one of the two exposed package walls (5a) of the package sleeve (1) on the removal side (7) of the magazine (2) (cf. FIG. 1a)). A suction gripper (9) fastened on a pivot arm (11) disposed pivotably about an axis (10) is used to grip the package wall (5a). As a result of a pivoting movement of the suction gripper (9) executed about the axis (10), the outer fold edge (3a) is initially released from the retaining element (8a), whereby during the subsequent pivoting movement of the suction gripper (9) about the opposite outer fold edge (3b), which is still held by the retaining element (8b), a flat parallelogram is formed as can be identified in particular from FIG. 1a). In the course of the further pivoting movement, the outer fold edge (3b) is initially released from the retaining element (8b). The package sleeve (1) with the other of the two exposed package walls (5b) is then guided slidingly along a curved guide surface (12) of a guide element (13). During the movement of the package sleeve (1) along the movement path (14) the guide surface (12) brings about an increase in the acute internal angles (15a, 15b), where the internal angle (15a) is enclosed between the package walls (5b, 6b) and the internal angle (15b) is enclosed between the package walls (5a, 6a). Located at the end of the curved guide surface (12) in the direction of the movement path (14) is a retaining element (16) that is introduced into the guide element (13) in the form of a groove-shaped recess. The retaining element (16) is used to receive the outer fold edge (3b) of the unfolded package sleeve (1). Located likewise in the direction of the movement path (14) after the guide surface (12) is another fixed retaining element (17) in the form of a retaining strip (17) for receiving the diametrically opposite outer fold edge (3a). The spacing and the alignment of the retaining elements (16, 17) is accomplished in such a manner that the package sleeve received by the retaining elements (16, 17) forms a rectangle in cross-section. This alignment is necessary for transferring the completely unfolded package sleeve to the transport device located downstream of the removal and unfolding apparatus such as in particular the transport wheels mentioned initially.
Since the package sleeves (1) have been stored or transported for a long time in the flat-folded state before introduction into the machine, the fold edges (3a, 3b, 4a, 4b) of the package sleeve (1) give rise to restoring forces which counteract the unfolding of the package sleeve (1). The restoring forces increase with the unfolding of the initially flat-folded package sleeve (1) to form a parallelogram in cross-section, in particular a package sleeve forming a rectangle.
In order to reduce the restoring forces, the package sleeves (1) are moved somewhat beyond the rectangular cross-section with the aid of the sucker at the end of the curved guide surface (12) so that the initially acute internal angle (15a, 15b) of the package sleeve is briefly slightly more than 90°, as can be seen from FIG. 1c).
The package sleeve (1) can thereby be overstretched in the unfolded fold edges (3a, 3b) so that after erecting, the package sleeve (1) adopts and retains the desired rectangular or square cross-section (FIG. 1d)) as accurately as possible.
The overstretching of the fold edges is, however, only successful to a limited extent since the package sleeve must be overstretched a little more or a little less depending on the condition of the cardboard. However, as a result of the constant movement path (14) of the suction gripper (9), an individual overstretching is not possible. In addition, the additional movement of the suction gripper (9) for the overstretching takes time, thus lengthening the removal and unfolding cycle. This lengthening of the cycle reduces the working speed of the entire filling machine.
In order not to restrict the speed of the filling machine too severely despite the overstretching, the package sleeves are removed and unfolded at the highest possible speed. As a result, a large amount of noise is generated when the fold edges (3a, 3b) snap into the retaining elements (16, 17).
EP 0 978 453 A discloses a removal and unfolding apparatus for the removal of a flat-folded package sleeve from a magazine and for unfolding the removed package sleeve, which transfers the package sleeve, which is partially erected in cross-section to form a parallelogram, to a transport device comprising two revolving belts for transporting the upright package sleeve along a transport path. During the transfer to the transport device, the package sleeve is briefly overstretched by means of a folding means which is pivotably disposed on the removal and unfolding apparatus. The restoring forces are reduced by the overstretching.
EP 0 356 824 A1 discloses a method for unfolding a flat-folded package sleeve by means of an erecting apparatus in which the flat-folded package sleeves are introduced by means of a lifting conveyor between discharging rollers and conveyed obliquely upwards. With the aid of a pushing device and supports, the flat folded package sleeve is unfolded in the erecting apparatus, where the internal angles between the package walls at the outer fold edges are increased to approximately 180°. This results in a reduction in the restoring forces. The pushing device is then moved away from the side of the discharging rollers, where the pushing device adopts a central position so that the package sleeve relaxes to a square cross-section and retains this. An unloading conveyor device then pushes the package sleeve which has been erected to a square cross-section, onto a mandrel wheel.
EP 0339 116 A2 discloses a method for reducing restoring forces of package sleeves in a carton erecting apparatus, where the flat-folded package sleeves are removed individually from the magazine by means of a revolving conveyor with suction cups and are erected by means of guide elements to form a package sleeve forming a rectangle in cross-section. The conveyer transfers the upright package sleeve directly to means for reducing the restoring force which comprises two revolving upper conveyor belts and two revolving lower conveyor belts with projections disposed thereon. The two upper conveyor belts form a tapering shaft on the inlet side which has the effect that the internal angles between the package walls are increased to 180° at the outer fold edges whilst the package sleeve runs through the shaft. The package sleeve folded flat in such a manner then enters a station for re-erection of the flat-folded package sleeve. After re-erection of the flat-folded package sleeve, said sleeve is passed onto an unloading conveyor which conveys the upright package sleeve to a filling machine.
DE 933 918 B discloses an apparatus for reducing the restoring force of an upright package sleeve in a filling machine, in which the flat-folded package sleeve is removed from a magazine from below with the aid of a removal sword and erected to a package sleeve forming a rectangle in cross-section. In order to reduce the restoring force, a stress-relieving straight edge is applied to the surface of the upright package sleeve, which executes a swinging movement about the lower fold box edge. During the reduction of the restoring force, the removal sword holds the upright package sleeve firmly on a base and specifically until the package sleeve is completely folded flat by the stress-relieving straight edge. The package sleeve is then transported further with the aid of a conveying means.
U.S. Pat. No. 5,007,889 A discloses an apparatus for removing and unfolding a flat-folded package sleeve from a magazine, where the unfolding of the package sleeve is accomplished by means of an unfolding arm. During the removal of the package sleeve by means of suction grippers disposed on a pivoting arm, the restoring force of the package sleeve is simultaneously reduced, since the internal angle θ is temporarily increased to more than 90° by means of the unfolding arm.